Rotary pump and motor hydraulic transmission system



June 3, 1952 w, w, HENNlNG 2,599,450

ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION SYSTEM Filed June 20, 1947 IN V EN TOR.

Ufilhlam Uf. Hennily Paltented June 3, 1952 QFFICE ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION SYSTEM William W. Henning, Riverside, IIL, assignor to International Harvester Company, a corporation of New Jersey Application June 20, 1947, Serial No. 756,074

This application concerns hydraulic power transmitting systems for transmitting driving force from a vehicle engine to propelling units of the vehicle, and relates more particularly to hydraulic braking means associated with the system for preventing uncontrolled vehicular movement.

It is customary in hydraulic power transmitting systems for vehicles to provide an engine driven pump for supplying propelling fluid to a hydraulic motor connected with traction wheels or the like of the vehicle. it has also been contemplated to employ a variable capacity pump as an expedient for varying the speed at which the motor and the traction means are driven. In the operation of a vehicle driven by a hydraulic system of the character just referred to, there are times when the motor will be caused to op erate as a pump. Such condition arises when, for example, the vehicle is proceeding downhill andthe variable capacity pump is adjusted to a non-delivery condition. The inertia of the vehicle, and sometimes of a load coupled therebehind, will then cause the unit normally acting as a motor to act as a pump-and, if the inertia of the vehicle and load is large, the resistance offered by the motor then operated as a pump will not be sufficient to oppose the vehicular movement. Such resistance of the motor to vehicular movement has been heretofore augmented by means of a throttling or braking valve in the exhaust line of the motor.

The principal object of this invention is the provision of an improved braking valve of this character, and hydraulic controls for this valve.

A more specific object is the provision of a novel hydraulic braking unit including a braking valve closable when a plungerwithin the unit is moved in one axial direction, a chamber receivable of fluid for urging the plunger in the valve closing direction, a bore extending axially through the plunger for providing communication between the chamber and the outlet of the vehicle motor, and a second chamber communicative with the high pressure section of the hydraulic power transmitting system for receiving fluid therefrom under pressure actable upon a portion of the plunger for moving it in the opposite direction for opening the valve, whereby the braking valve will have no throttling effect upon the output of the motor when power is being transmitted from the pump to such motor.

The above and other desirable objects inherent in and encompassed by the invention will become more fully comprehended after, reading 4 Claims. (CI. 60-53) the ensuing description with reference to the annexed drawing, wherein The single figure is a view, principally diagrammatic, illustrating a preferred form of the invention incorporated into a power transmitting hydraulic circuit installed between an engine and propelling treads of a crawler tractor.

With continued reference to the drawing, there is diagrammatically shown an engine E of a crawler tractor having endless propelling treads or units 1 I at opposite sides of the vehicle. These treads H are driven by respective drive sprockets it which are constrained for rotation with gears 23. Driving pinions I4 respectively drivable by hydraulic motors M-l and M-2 are in meshed driving relation with the gears 3. The units H are positively connected with their respective motors M-l and M-2 through the gearing l2- 13-4 3, wherefore hydraulic retarding of the mo tors has a braking action on said units which therefore constitute propellable and brakable units.

When the hydraulic motors M-l and M-2 are driven at the same speed, the two propelling units I will be driven at the same speed and cause the vehicle to proceed along a straight course. Simultaneous variation in the speed of motor M4 and M-2 in like amounts will change the speed of the vehicle in a straight course, whereas operation of the motors NH and M-Z at different speeds will cause the propelling units H to operate at different speeds and change the course of the vehicle from the straight line course.

A hydraulic system for controlling the speeds of the motors M-! and M-2 and for transmitting driving force thereto from the engine E includes pumps PI and P2 having their driving elements coupled to an engine driven shaft l5. Each of the pumps is of variable capacity and has a capacity varying control element It operatively connected thereto by diagrammatically shown connections H. It will be assumed that, when either control element It occupies a position at the C limit of its adjustable range CH, the associated pump P! or P2 will be adjusted for causing zero output of fluid; that when the element i8 is moved to the H limit of its adjustable range, maximum output of the associated pump will be attained and that adjustments in between the range limits C and H will cause pump delivery proportional to the distance the element is moved from the limit C toward the limit H.

Pump P! has an inlet l8 communicating with a reservoir tithrough conduits, I9 and 2!; Outreservoir 35 through conduits 36 and 3'! respec- 1 tively, including a cooler 38 and a filter 33. Con.-

duit 36 contains a passage constricting unit' 'lli for increasing the amount of oil flowing through the filter. A pressure relief -valve-42.- is also con.-

nected between the conduit Stand-the reser-" voir 35.

A high pressure section of the system cornprises conduits 24 and 21 an'd'also conduits 44 and 43 which lead respectively to a pressure relief valve 45 and a control chamber 18 of the braking unit 10. Another conduit 41-commu-nicatesbetween the discharge end-of the pressure'relief valve 45 and the conduit-'34. V

Fluid for the-pump P2 entersits-inlet' 48 from the'reservoir 35 throug h the conduit I9--and a conduit 49. Theoutlet 5| of thepumpcommunicates with an inlet 23' of the motor M-.2 through -a conduit 24', check valve- 25' and-conduits 26' and 2.1. Those-partsassociated with the." output of the pump-P2 and designated by the referencecharaoter includin a prime correspond-respectively to elements associated with the output of pump PI designated by the same reference characters, withoutthe prime. Check valves '60 and B are. communicativelyconnected between the-low pressure'conduit '34 and the motor inlets 23 and -23',- respectively.

Since, the-hydraulic braking units 1.0 and 10' are'identical, only the unit I0 is hereinillustrated anddescribed-indetail. Thisunit 10 comprises a. casing; H slidably containing a plunger 12 wherein there is a bore 13 extending between opposite, ends. The braking valve 2 9- at the left end-of the casing is closed by the'plunger 12 when it'is allowedto-be'moved to the-left under the force of a spring 14 in a spring chamber-1 5. The valve 29 is in series with a cha-mber like passage-55 between the conduits;

32- and 33. A fluid operateddev-ice comprisinga cylindrical enlargement 16 on an intermediate portion-of the plunger 12 is adapted to move the plunger to the right in opposition to-the spring 14 when fluid is introduced into the annular control chamber l8 through theconduit 43. Thepressure-of fluid in the conduit'32 is transmitted through the plunger bore 13 into the spring chamber 15 and thereby diminishes the amount of force necessary to be exerted by the spring 14 and consequently the size of such spring. Fluid which may leak from the spring chamber 15. past a bearing 19 for a reduced diameter end portion 80 of theplung'er I2 is caught inchamber Blfrom which it is drainable through 'a-conduit 82 into the low pressure section of the system. A similar conduit 83 is. provided for achamber 84 intov which fluid may leak from the control chamber 18 past the enlarged piston port-ion 16 of the plunger.

Operation of the apparatus 'The-partsare illustrated in the positions occupied when the-vehicle is being driven at a moderate speed along a straight course. Eachof'the control levers lG-is substantially -'m-idway of its adjustable range whereby 1 the pumps P| and 92 4 are caused to deliver fluid at a moderate rate. so long as the vehicle is traveling under load conditions, that is, under conditions requiring power from the engine for driving the propelling units H, fluid from the pump Pl will be under high pressure and in passing through the motor M-l from its; inlet 23 to, its outlets will-cause operation of this motor and "ofv its, propel-ling unit H. Fluid discharged from the motor outlet 28 will be 'cjonducted through the conduit 32 to the valve 29 and past this valve through the chamber passage "'55to-thefconduit-33 for ultimate delivery into tlie'reservoir 35. "conduit-'43,whichis part of the high pressure section of thehydraulic system, is imposed into The high pressure fluid in the the braking'iinit -chamber 18 where sufiicient pressure is, developed thereby for moving the piston-'lflenlargement I6 and the valve plunger 1.2 to'the right while compressing the spring 14. The valve 29 will thus be widely opened so as to avoid-having -a throttling efiect: upon the fluid dischargedtrom the motor-outlet 28 duringthe transmission of'power from the. pump to the motor- M- I. This same-condition. prevails onthe right sideofthe vehicle with respect to the'pump P2, the motor M-2- and the hydraulic motor brake.

unit 18.

Assume now that the vehicle is towing loaded trailer, and assume thatthis -vehicle-train'com, mences to descend a grade-of suiiicientsteep ness that inertia-of the train-would cause it-to proceed-at a speed-in excess of thedesiredspeed. Under thesecircumstances the-operator WllL-SQQ the control levers I'S-inapositioneausing fluid delivery to the pumps Pl and Phat arate-correspending to the-desired rate of vehicle travel. Pressure in the normally highpressure section of the system, including; the conduits24and-43, will thereupon drop,-enabling the spring l4-of-the hydraulic braking-unit?!) to place the-valve 29- in a throttling-condition creating; resistance to discharge of -fiuid from the motor M-l' and consequently creating a braking effect upon the, vehicle. Thesame action will be taking place for the motor M-2 and its braking unit 10 Should the operator flnd-that the-vehicle-train is descending-the-- grade at=greater-speed than desired, he will simply move; the control members t6v further toward the C limit of their-adjustablerange to diminish the output ofvthe; pumps PI and- P2, thereby further diminishingthe pressure in the conduits43 and 43' and the braking unit chambers 18 and-l8, whereby thesprings'as 'Mcanpress the valves as 29 into an-increased throttling relation with corresponding greater brakingeffect. With this system of-pressure responsive fluid braking, there is effected automatic braking action which causes the-vehicleto proceed downhill without gaining any speed and without the necessity of the operator applying a brake or changing the setting of the hydraulic Normally, the check valves 60 and-6,0 will re main-closed. Their sole purpose is to establish communication between the low pressure section of the system-and their respectivelyassociated high pressure section-for supplying fluid to the inlets-of motors M|- and M-2 to prevent starvingof the inlets of these, motors under an emergency condition where the vehicle trainmay be descending a grade of sufficient-steepnessto cause the vehicle train tocontinue moving, subseqiTeTi't to movement-ofthe'control'levers 16 to the position causing-nol delivery of'the pum'ps Pl andPZ forthe? purpose of stopping the same. If the tutput of the pumps PI and P2 should be stopped and the momentum of the vehicle should continue to carry it along the course, the motors M-i and M-2, then operating as pumps, would very quickly empty themselves and the high pressure sections of the system of fluid so there would be none to discharge past the braking valves as 29 (assuming the valves 60 and 60 not present), so that substantially all braking resistanec would be lost. However, this condition cannot prevail when the valves 60 and 6B are installed, since the motors M-l and M-2, operating as pumps, would draw fluid through these valves from the low pressure section of the system for pumping past the braking valves as 29. The vehicle would normally be supposed to stop when the control levers l6--l6 are moved to the position C causing the pumps p and p to deliver and receive no fluid. Consequently, the springs as H3 in the braking devices 10 and 10', when unopposed b the pressure of fluid from these pumps into the chambers as 18, will prevent discharge of fluid past the valves excepting by abnormal pressure of fluid discharged by the pump-operated motors, Ml-MZ. ing the valves as 29 under these circumstances reaches the low pressure side of the system through the conduits 3233.

Having thus described a preferred embodiment of the invention with the View of clearly and concisely illustrating the same, I claim:

1. In a hydraulic power transmission system for driving a propellable and brakable unit, a variable capacity pump having an inlet communicative with a low pressure section of said system and an outlet connected with a high pressure section of such system, a hydraulic motor drivingly connected with said unit, said motor having an inlet connected with the high pressure section of the system and an outlet connected with the low pressure section of the system, a braking valve interposed between the outlet side of the motor and the low pressure section of the system, means including a fluid operated device energized by the pressure of fluid discharged from the motor outlet tending to close said valve, means responsive to the transmission of fluid under pressure from the pump to the motor for opening the braking valve, and a check valve connected between the motor inlet and the low pres- I sure section of the system for supplying fluid to the motor independently of the pump.

2. In a, hydraulic power transmission system for driving a propellable and brakable unit, a variable capacity pump having an inlet communicative with a low pressure section of said system and an outlet connected with a high pressure section of such system, a hydraulic motor drivingly connected with said unit, said motor having an inlet connected with the high pressure section of the system and an outlet connected with the low pressure section of the system, a braking valve interposed between the outlet side of the motor and the low pressure section of the system, said valve being operable to resist discharge of fluid from the motor outlet and thereby serve as a motor brake, means responsive to the transmission of fluid under pressure from Fluid pass- 6 the pump to the motor for contravening the braking function of the braking valve, and brake valve control means operable responsively to the pressure of fluid transmitted from the motor outlet to the brake valve for tendin to establish the braking function of such valve.

3. In a hydraulic power transmission system for driving a propellable and brakable unit, a pump having an inlet communicative with a low pressure section of said system and an outlet connected with a high pressure section of such system, a hydraulic motor drivingly connected with said unit, said motor having an inlet connected with the high pressure section of the system and an outlet connected with the low-pressure section of the system, a hydraulic braking unit comprising a casing, a fluid-conducting passage extending through said casing and connected between the motor outlet and the low pressure section of the system, a braking valve in said casing in series with said passage and comprising a plunger movable endwise in one direction for at least partly closing such valve and thereby throttling the flow of fluid through the passage to produce a braking action for the motor, said plunger having a section having an annular enlargement circumscribing the same, said casing having an annular control chamber circumscribing said plunger section and adapted to receive fluid under pressure for exerting a force against said plunger enlargement for moving the plunger in the opposite direction to open said valve, said plunger having a reduced diameter end portion,

said casing having a spring chamber receiving the reduced end portion of the plunger and adapted to receive pressure fluid for exerting a force against the plunger to urge the same endwise in the one direction for closing the valve, a spring in said spring chamber to urge the plunger in the one direction, conduit means communicating between the spring chamber and the motor outlet, and conduit means communicating between the high pressure section of the system and said control chamber.

4. The combination set forth in claim 3, wherein the end of the plunger opposite from the reduced diameter end portion is subjected to the pressure of fluid discharged from the motor outlet to urge the plunger in the axial direction for opening said valve, and wherein the conduit means communicative between the sprin chamber and the motor outlet includes an axial bore through the plunger.

WILLIAM W. HENNING.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 1,111,994 Ciarlo Sept. 29, 1914 1,307,819 Janney June 24, 1919 1,615,341 Murray Jan. 25, 1927 1,970,181 Monroe Aug. 14, 1934 2,275,321 Scates Mar. 3, 1942 2,335,305 Parsons Nov. 30, 1943 

